Ambient air in homes, offices, manufacturing facilities and other workplace environments is often contaminated with biological and chemical contaminants. Many germs and viruses can be spread by airborne vectors. Additionally, molds, fungi, and pollens can be circulated over wide areas by air currents. Trace amounts of chemicals contained in building materials, carpets, machinery, and cleaning products regularly diffuse into the ambient air. These biological and chemical contaminants can cause discomfort to individuals ranging from relatively mild allergic reactions to serious illnesses. Often only trace amounts of these contaminants are required to cause such undesirable reactions. For example, certain chemicals present in new carpets in only a few parts per million (PPM) can cause considerable discomfort. Besides causing discomfort and illness to individuals, such contaminants can also have serious quality-control implications in manufacturing facilities, particularly in high tech and pharmaceutical manufacturing operations. As buildings become better insulated, the quality of the indoor air often becomes worse, because the air exchange rate (the rate at which the internal volume of air is replaced by fresh air from outside the building) is frequently much lower for “tight,” well-insulated buildings compared to drafty, less well-insulated buildings.
There are several known methods for removing or destroying chemical species from contaminated air, including adsorption by carbon, photocatalytic oxidation, thermal oxidation, and thermocatalytic oxidation. Similarly, known methods for removing or destroying airborne biological particulates include filtration, photocatalytic oxidation, and thermocatalytic oxidation. Apparatus useful for employing these methods are also well known in the art.
While the forgoing methods (and their associated apparatus) are suitable in certain instances, they may not be desirable in all applications. For example, a specific air filtration device may remove certain types of toxic biological organisms, such as bacteria, while not removing other toxic organisms, such as viruses, or may not be able to reduce the concentration level of a particular toxic species to an acceptable level. Furthermore, the devices used to implement a specific conventional method may require heavy or bulky equipment that is impractical for use in all applications. In particular, air purification units that rely on filtration or carbon adsorption suffer from the disadvantage of requiring frequent maintenance to replace clogged filters or spent carbon. Carbon adsorption filters in particular suffer from the disadvantage that adsorbed contaminants can be de-sorbed back into the environment from which contaminants are intended to be removed, particularly, when the level of contaminants in the environment is low compared to the level of contaminants that has been adsorbed by the carbon.
Prior art apparatus that destroys airborne contaminants by oxidation does not require ongoing maintenance, unlike filter-based systems. However, prior art thermocatalytic oxidation systems are generally large, bulky and thermally inefficient units. It would thus be desirable to provide thermocatalytic and thermal oxidation air purification units that are compact and have a high thermal efficiency. In particular, it would be desirable to provide a unit in which the thermal treatment unit is integral to the heat exchanger, to reduce the number of seals required, and to increase the efficiency of such a system. A device that integrates a heat exchanger with thermal treatment components is not described in the prior art.